1. Field of the Invention
The present invention relates to a probe device for inspecting circuits of such electronic devices as semiconductor wafers, semiconductor integrated circuit chips and liquid crystal devices whose circuit terminals (pads) are arranged two-dimensionally, and more particularly to a probe device for making electrical connections between two electronic devices or for electrically connecting to a socket of a chip-size package (CSP) whose pads are arrayed two-dimensionally.
2. Description of Prior Art
With the advance of semiconductor manufacturing technologies, a degree of integration of electronic devices improves, resulting in an increase in an area occupied by interconnect wiring in semiconductor chips formed on a semiconductor wafer, which in turn increases the number of pads on each semiconductor chip. This leads to reductions in an area of each pad and in a pad pitch, thus accelerating a miniaturization of pad arrays. At the same time, connection terminal arrays of a socket used to inspect the CSPs are also being miniaturized.
A problem arising from the miniaturization of the pad arrays (reduced pad pitch) is that, in performing electric characteristic tests and circuit inspections on electronic devices, a structure of contacts or probes that are brought into contact with associated pads of a semiconductor chip to achieve electric conduction needs to be reduced in size to match the miniaturization of the semiconductor chip. A variety of means are available that help the probes meet requirements imposed by the miniaturized pad arrays.
For example, there is a means that interposes between pads of a semiconductor chip to be inspected and an inspection apparatus a probe assembly comprising a plurality of two-dimensionally arranged probes which are each made from a thin plate material and elastically deformable when applied an external force (Japanese Patent Disclosure No. 2001-091537). As a means for making an electrical connection between such a probe assembly and a semiconductor chip test circuit, a printed circuit board called a probe card has conventionally been used.
In a probe card of cantilever type that employs needle-shaped contacts or probes, although tip portions of the probes in contact with pads of a semiconductor chip are narrow in pitch, root portions of the probes connected with terminals of the probe card can be made coarse in pitch, so that the probes can be securely connected, as by soldering, to the terminals of the probe card for electric connection.
On the other hand, in a probe card disclosed in Japanese Patent Disclosure No. 1-189932 in which probes are vertically fixed to terminals of a printed circuit board (hereinafter referred to as vertical probes) and thus subject to a vertically acting force, it is required that a pad pitch on a semiconductor chip and a terminal pitch on the printed circuit board or probe card be equal. However, on the printed circuit board it is difficult to micro-fabricate a circuit pattern and thus the area of each terminal and the width of each wire are inevitably wide. Hence, as the level of miniaturization progresses, vertically securing the vertical probes to the printed circuit board while keeping the probe pitch aligned to the pad pitch of the semiconductor chip becomes increasingly difficult.
As described above, in the printed circuit board or probe card a two-dimensional area is occupied by metal wires in addition to probes and terminals, which basically act to hinder the miniaturization of the printed circuit board to match the ever decreasing pad pitch of semiconductor chips. For those chips whose pads are arranged in a lattice formation or in staggered columns, a method is available which employs a multilayer printed circuit board as a means to achieve an electric connection from inside pads to outside circuits. The multilayer structure, however, requires through-holes (vertical holes piercing the wiring board) that make electrical connection between different layers, and a space occupied by the through-holes becomes an obstacle to reducing the pitch of arrayed terminals.
Another connection method, which can deal with the lattice area array type vertical probes, connects the probes and the printed circuit board by soldering wires. However, there is a limit to the reduction in the pitch of the probes and terminals at which they can be soldered with wires, and the number of wires has already reached the limit. As described above, not only are further reductions in the pitch difficult to achieve with these methods but they also require a large number of processing steps, which in turn leads to increased cost.
According to one aspect, the present invention provides a probe device for making electrical connections between a semiconductor chip to be inspected and an inspection device through probes by bringing the probes into contact with the semiconductor chip, the probe device comprising: a probe assembly made up of a plurality of regularly arrayed vertical probes; a flexible flat cable having metal lines formed and bonded to a surface of a non-conductive flexible film; and a fixing device for fixing one end of the flexible flat cable; wherein metal line terminals formed at the one end of the flexible flat cable secured to the fixing device are put in contact with the probe assembly, metal line terminals formed at the other end of the flexible flat cable are connected to a printed circuit board or a connector, and the semiconductor chip to be inspected and the inspection device are electrically connected together through the probe assembly, the flexible flat cable and the printed circuit board or connector.
According to another aspect of the invention, the regularly arrayed vertical probes vertically contact end faces of the metal line terminals formed at the one end of the flexible flat cable; an arrangement of the metal line terminals formed at the one end of the flexible flat cable corresponds to an arrangement of the regularly arrayed vertical probes; an arrangement of the metal line terminals formed at the one end of the flexible flat cable is a line array; and a plurality of the flexible flat cables each having line-arrayed metal line terminals at the one end thereof are gathered to form an area array of the metal line terminals.
According to still another aspect of the invention, the metal line terminals formed at the one end of the flexible flat cable protrude slightly from one end face of a non-conductive flexible film forming the flexible flat cable; and the flexible flat cable is shaped like a strip having a narrow-width portion at one end and a wide-width portion at the other end, and narrow-pitch metal lines formed in the narrow-width portion and coarse-pitch metal lines formed in the wide-width portion are connected.
According to a further aspect of the invention, the fixing device for fixing the flexible flat cable having the metal line terminals facing line-arrayed vertical probes includes: a fixing block having a plurality of vertical surfaces; a clamper for pressing a narrow-width portion formed at the one end of the flexible flat cable against the vertical surfaces of the fixing block, with end faces of the metal line terminals facing up, to securely hold the flexible flat cable; and a moving mechanism for the clamper. The metal line terminals of the flexible flat cable facing the line-arrayed vertical probes are arrayed in line along an upper side of each of the vertical surfaces of the fixing block, with tips of the metal line terminals slightly protruding from the upper sides of the vertical surfaces.
According to a further aspect of the invention, the fixing device for fixing the flexible flat cables having the metal line terminals facing area-arrayed vertical probes includes: a flat metal line separation and fixing device having a plurality of slits; and a flat metal line positioning and fixing device installed over the flat metal line separation and fixing device and having columns of small holes formed therein at positions facing the slits; wherein narrow-width portions of the flexible flat cables are passed from under the flat metal line separation and fixing device through the slits and then the metal line terminals are passed into the small holes, thereby securely holding the flexible flat cables. The metal line terminals of the flexible flat cables facing area-arrayed vertical probes are arrayed, with their tips slightly protruding from the small holes of the flat metal line positioning and fixing device. The small holes formed in the flat metal line positioning and fixing device are arrayed in a lattice formation or in staggered columns.
According to a further aspect of the invention, the flexible flat cable has one end thereof secured to the fixing device and the other end passing under the fixing device and connected to connection terminals of the printed circuit board or connector. The probe device further includes a probe connection structure constructed of the flexible flat cable and the fixing device securely holding the flexible flat cable, the flexible flat cable having line-arrayed or area-arrayed metal line terminals.
As described above, the probe device of this invention produces the following effects by taking advantage of the functions of the FFC. That is, a probe connection structure that forms a connection point for the vertical probes can be assembled by simply holding one end of each FFC to the fixing device and using the end faces (cut faces) of the narrow-pitch terminals on the FFCs for connection with the probes. Further, by converting the pitch of the metal lines connecting to this connecting point from a narrow pitch at one end of each FFC to a coarse pitch at the other end, a connection can easily be made between the metal lines and a printed circuit board or a connector.
Further, the probe device of this invention can be used for a wide range of applications, which include circuit inspections on semiconductor wafers, semiconductor integrated circuit chips and liquid crystal devices whose circuit terminals (pads) are arranged two-dimensionally at a narrow pitch, electrical connections between two electronic devices by using the connector functions, and also electrical connections to a socket of CSP whose pads are arranged two-dimensionally.
It is therefore a first object of the present invention to provide a probe device which uses vertical probes developed to comply with a reduced pitch of pads on semiconductor chips and which can make correct connections between the vertical probes assembled at a reduced pitch and connection terminals of a printed circuit board or connector formed at a conventional coarse pitch.
A second object of the present invention is to provide a probe device that can facilitate electric characteristic inspections on semiconductor chips with reduced-pitch pads.
A third object of the present invention is to provide a probe device having multiple functions so that it can be used also as a connector for connection with a CSP socket and for connection between two electronic devices.
These and other objects and advantages of the present invention will become more apparent from the following description of embodiments thereof taken in conjunction with the accompanying drawings.